Cross-links are junctions of polymer strands in a three-dimensional network. They may be viewed as long-chain branches which are so numerous that a continuous insoluble network or gel is formed.
Platinum catalyzed hydrosilylation reactions have been used to form networks. Typically, such reactions involve a low molecular weight siloxane containing .tbd.Si--H groups, and a high molecular weight siloxane containing .tbd.Si-vinyl groups, or vice versa.
Attractive features of this mechanism are that (i) no by-products are formed, (ii) cross-linking sites and hence network architecture can be narrowly defined, and (iii) hydrosilylation will proceed even at room temperature to form the networks. In the mechanism, crosslinking involves addition of .tbd.SiH across double bonds, i.e., .tbd.SiH+CH.sub.2 .dbd.CH--R.fwdarw..tbd.SiCH.sub.2 CH.sub.2 --R; or crosslinking involves addition of .tbd.SiH across triple bonds, i.e., .tbd.SiH+HC.tbd.C--R.fwdarw..tbd.SiCH.dbd.CH--R.
We have utilized this mechanism, but by employing some unobvious and unique modifications of the mechanism, we have been able to formulate a new range of product forms having new and unique properties and ranges of application.
In particular, one unique aspect is that our silicone paste can be used to form an emulsion without the need of a surfactant. This can be of considerable value in the personal care arena where skin sensitivity due to the presence of certain surfactants can be an issue.